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No description available.

If the privatization of space telecommunications, because of its impacts, has been subject to various studies, this thesis focuses the analysis of this phenomenon on a particular point: its implications on international organizations. / Because of the evolution of the sector, international satellite organizations have undertaken for around ten years several internal reforms that lead today to the privatization of the three major organizations: Intelsat, Inmarsat and Eutelsat. These transformations constitute a particular sensitive issue as these organizations have been initially established so that to exploit satellite systems for the general interest of their members. / The impact of this phenomenon is no less considerable on the ITU, in charge of the international regulation, from a regulatory but also structural point of view. Moreover, the liberalization of telecommunication market undertaken under the aegis of the WTO grants to this organization a new major place in space telecommunication regulation.

Land Mobile Satellite Systems (LMSS) generally differ from other terrestrial wireless systems. The LMSS exhibit unique characteristics with regard to the physical layer, interference scenarios, channel impairements, propagation delay, link characteristics, service coverage, user and satellite mobility etc. Terrestrial wireless systems have employed the spatial diversity or MIMO (Multiple Input Multiple Output) technique in addressing the problem of providing uninterrupted service delivery to all mobile users especially in places where non-Line-of-Sight (NLoS) condition is prevalent (e.g. urban and suburban environments). For the LMSS, cooperative diversity has been proposed as a valuable alternative to the spatial diversity technique since it does not require the deployment of additional antennas in order to mitigate the fading effects. The basis of cooperative diversity is to have a group of mobile terminals sharing their antennas in order to generate a “virtual” multiple antenna, thus obtaining the same effects as the conventional MIMO system. However, the available cooperative diversity schemes as employed are based on outdated channel quality information (CQI) which is impracticable for LMSS due to its peculiar characteristics and its particularly long propagation delay. The key objective of this work is therefore to develop a cooperative diversity technology model which is most appropriate for LMSS and also adequately mitigates the outdated CQI challenge. To achieve the objective, the feasibility of cooperative diversity for LMSS was first analyzed by employing an appropriate LMSS channel model. Then, a novel Predictive Relay Selection (PRS) cooperative diversity scheme for LMSS was developed which adequately captured the LMSS architecture. The PRS cooperative scheme developed employed prediction algorithms, namely linear prediction and pattern-matching prediction algorithms in determining the future CQI of the available relay terminals before choosing the most appropriate relay for cooperation. The performance of the PRS cooperative diversity scheme in terms of average output SNR, outage probability, average channel capacity and bit error probability were simulated, then numerically analyzed. The results of the PRS cooperative diversity model for LMSS developed not only showed the gains resulting from introducing cooperative techniques in satellite communications but also showed improvement over other cooperative techniques that based their relay selection cooperation on channels with outdated quality information (CQI). Finally, a comparison between the results obtained from the various predictive models considered was carried out and the best prediction model was recommended for the PRS cooperation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

The objective of this study is to develop a general understanding of the evolution of the commercial communication satellite industry. Initial information classifies the industry as an oligopoly with the vendors as price setters. The approach to this thesis is to examine the supply and demand of satellites as a capital good. Assuming the demand curve slopes downwards, the study examines the change in the price of a standard unit satellite. The underlying motivation is the conventional identification problem. Over three generations, the technical attributes of communication satellites are advancing. Taking the hedonic regression approach, the price of satellites is shown to decrease over time. Exploring the relationship between price and complexity, it is demonstrated that in the short-run the oligopoly structure of this industry is accompanied by a simple form of cost-plus price-setting. This finding solves the identification problem, so that simultaneous equation methods are not required. Assuming a constant degree of monopoly power in the industry, changes in multi-factor productivity are estimated. Productivity growth increases until 1980, but decreases slightly afterwards. The learning coefficients estimated for this industry are smaller than those found for the airframe industry. The fall in quality-corrected prices, however, is not big enough to support the interpretation that the expansion of satellite capacity was due to supply shifts along a stationary market demand schedule. Factors driving demand lead to a faster rate of expansion outside the original western world, but in the second half of the period, the ability to use software data compression moderated the rate of growth of demand for new satellites. The study explains the adjustment of the stock of satellite capacity in response to the desired stock: the speed at which countries adjust their stock depends on their characteristics and regional profile.

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In 2004, President Bush addressed the nation and presented NASA's new vision for space exploration. This vision included the completion of the International Space Station, the retirement of the Space Shuttle, the development of a new crew exploration vehicle, and the return of humans to the moon by 2020. NASA's Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely. This architecture requires the development of two new Shuttle-derived launch vehicles, an in-space transportation vehicle, a lunar descent and landing vehicle, and a crew exploration vehicle for human transportation. The development of an in-space propellant transfer capability could greatly improve the performance, cost, mission success, and mission extensibility of the overall lunar architecture, providing a more optimal solution for future exploration missions. The work done in this thesis will analyze how this new capability could affect the current NASA lunar architecture, and will outline the value proposition of propellant refueling to NASA. A value proposition for propellant refueling will be provided to establish why an architecture that utilizes propellant refueling is better equipped to meet the goals of the Vision for Space Exploration than the current baseline design. The primary goal addressed in this research is the development of a sustainable and affordable exploration program. The value proposition will outline various refueling strategies that can be used to improve each of the architecture Figures of Merit. These include a decrease in the Life Cycle Cost of both the lunar and Mars exploration campaigns, the ability to more than double the mission payload that can be delivered to the lunar surface during cargo missions, improving the probability of successfully completing each lunar mission, decreasing the uncertainty, and therefore risk, experienced during the development process, and improving the extensibility of the exploration architecture by utilizing a greater portion of the lunar program for future crewed mission. The ability to improve these Figures of Merit provides NASA with a more valuable architecture because NASA is able to achieve a greater return on its large initial investment.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 92-93). / x, 93 leaves, bound ill. 29 cm

Thesis (PhD)--University of South Australia, 1999